Then a different taper seat "should be" a problem even if just on one bolt per wheel its not good.
Its to do with clamping forces locking wheel nuts are designed to have a lower clamping force at the same torque setting so the breakaway force is lower ( ie. The torque required to loosen the nut or bolt off again )
This is because the torque that can be applied to a locking wheel nut key before it shears or gets damaged is considerably less than the stock hex wheel nut.
This is deemed acceptable on a car as it has the other 3 or 4 fixings that are full on
(Also most cars wheels would not fall off with one missing fixing ( although this is an mot fail) so the force applied by the locker deemed acceptable.
But 4 on the one wheel could end up with a loose wheel somewhere down the road so as i said this is a potential issue.
Stephen.
Edit.
I would also say that not all locking wheel nuts are designed this way .
A lot of the MGard type locking wheel nuts fitted to modern cars are designed that way though.